This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Specific Aims (summary): Disorders that disrupt attention (e.g., dyslexia, ADHD) prevent proper stimulus sorting. This may be particularly detrimental to speech processing, due in part to: disrupted working memory, the acoustic characteristics of speech and the fact that sounds from multiple sources are combined as a single complex upon reaching a receiver. Thus, the long-range goals of this project are to understand 1) how an acoustic complex is deconstructed into its components so that sounds may be identified, grouped and assigned to their correct sources;and, 2) how such sorting and grouping is modulated by attention. There is presently no neuronal definition of attention in general and to speech in particular, as model systems rarely exhibit the processing shown by humans for speech. The proposed research tests the overall hypotheses that for speech-like sounds auditory groups are formed through comparisons between multiple cues and that the pre-cortical neural units responsible for such processing can be modulated by dopaminergic input to produce different grouping decisions. This research uses an animal model in which speech-like sounds are behaviorally relevant, there is a robust bioassasy for attention, and the brain is readily accessible through electrophysiological and molecular-marking techniques.